He curated important retrospectives of Mario Merz and Joseph Beuys, among others, at the Kunsthaus Zurich, as well as exhibitions in Vienna, Dusseldorf, Berlin, Rotterdam, Hamburg, Tokyo, and Bordeaux. (bard.edu)
The Museum of Modern Art (MoMA) in New York held two important retrospective exhibitions of Pollock's work - in 1956 and 1957. (visual-arts-cork.com)
There have been quite a number of ZERO exhibitions in recent years, including important retrospectives at the Solomon R. Guggenheim in New York, the Martin - Gropius - Bau in Berlin, and the Stedelijk... (mayorgallery.com)